The present invention relates to magnetic system, and more particularly to a method and system for providing magnetic tunneling junctions having improved reliability.
Because of their high magnetoresistance ratio, spin dependent tunneling sensors, otherwise known as magnetic tunneling junctions (MTJs), are currently of interest for use in a variety of devices, including magnetic memories such as magnetic random access memories (MRAM). FIG. 1 depicts a portion of a conventional magnetic memory, a conventional MRAM 1. The conventional MRAM 1 includes MTJs 10. Each MTJ 10 includes at least a conventional pinned layer 20, a conventional barrier layer 30 and a conventional free layer 40. The conventional barrier layer 30 is typically an insulator that serves as a tunneling barrier between the conventional pinned layer 20 and the conventional free layer 40. The conventional pinned layer 20 and the conventional free layer 40 are ferromagnetic. The magnetization of the conventional pinned layer 20 is pinned in a particular direction, generally by an anitiferromagnetic layer (not shown). The magnetization of the conventional free layer 40 is free to rotate in response to an external field. The conventional MRAM 1 includes a conventional bit line 60 and a conventional bottom lead 50. Current through the MTJ 10 is carried by the conventional bit line 60 and the conventional bottom lead 50. The magnetic MTJ 10 is switched using a combination of current driven through the bit line 60 and the magnetic tunneling junction 10 and the current through the corresponding digit line 70.
FIG. 2 is a diagram of a cross-sectional view of a portion of the magnetic memory 1. A magnetic tunneling junction 10 having the pinned layer 20, barrier layer 30 and free layer 40 are shown. The magnetic tunneling junction 10 is surrounded by an insulator (not explicitly shown). The magnetic tunneling junction typically includes an antiferromagnetic layer (not shown) and other layers, such as seed and/or capping layers. The bit line 60 is typically composed of a nonmagnetic conductive material, such as Cu. In order to switch the direction of magnetization of the magnetization of the free layer 40, current is driven through the bit line 60 and the digit line 70 (not shown in FIG. 2).
Although the conventional MRAM 1 functions, one of ordinary skill in the art will readily recognize that the conventional MRAM 1 consumes a great deal of power. In particular, a relatively large current is required in order to switch the magnetization of the free layer. As a result, a large amount of power is also consumed in order to switch the magnetization of the free layer 40. Consequently, the MRAM 1 utilizes a large amount of power when programming an MTJ 10.
Accordingly, what is needed is a system and method for decreasing the amount of power utilized by an MRAM. The present invention addresses such a need.
The present invention provides a method and system for providing a magnetic tunneling junction. The method and system comprise providing a free layer, a pinned layer, and a barrier between the free layer and the pinned layer. The free layer and the pinned layer are ferromagnetic. The barrier layer is an insulator. The magnetic tunneling junction is coupled to a bit line. The bit line includes a ferromagnetic liner and a nonmagnetic core. The nonmagnetic core includes a top, a bottom and sides. The ferromagnetic liner includes at least one tab and is adjacent to the sides and a portion of the bottom of the nonmagnetic core. The at least one tab is adjacent to the portion of the bottom of the nonmagnetic core.
According to the system and method disclosed herein, the present invention provides a magnetic tunneling junction that can be programmed using less power.